This invention relates to a pattern forming material, an acid precursor used therein, and a process for forming a pattern.
As to a pattern forming process comprising imagewise exposure to actinic radiation such as ultraviolet light to form an acid on a patterned latent image forming portion, changing the solubility for a developing solution of exposed portions and non-exposed portions to the actinic radiation by the reaction using the acid as a catalyst, and developing to form a pattern and pattern forming materials used therein, various proposals have been disclosed, for example, in U.S. Pat. No. 3,779,778, Japanese Patent Examined Publication Nos. 62-39420 and 62-39421, Japanese Patent Unexamined Publication Nos. 59-45439 and 62-164045, etc. These proposals include the use of highly reactive media in the presence of an acid catalyst and acid precursors which form an acid by exposure to actinic radiation. As the acid precursors, there are used various diazonium salts, various halogen compounds, various onium salts, etc. Since the diazonium salts are generally limited in conditions for stable use, there is a problem in their stability when used as the acid precursor in practicable usable pattern forming materials. As to the halogen compounds to there, is a problem of causing environmental pollution when they are used in large amounts as the acid precursor in industrially usable pattern forming materials. Further, as to the onium salts which have a good effect for lowering solubility for an alkali aqueous solution, usually used as a developing solution for forming fine patterns in semiconductor industry, there is a problem in that the control of pattern formation is difficult when a positive type pattern is formed by a development using an alkali aqueous solution.
Therefore acid precursors overcoming these problems mentioned above have been desired.